1. Field of the Invention
The present invention relates to a circuit and a method for driving a laser, and in particular, to a circuit and a method for driving a laser with temperature compensation function.
2. Description of the Related Art
With advances in light transmission technologies, fiber-optic transmission has great advantages in terms of transmission speed, transmission distance, and anti-interference ability, and thus optical transmission devices have become more and more popular. In an optical transmission device, light amplification by simulated emission of radiation (laser) components are usually used to convert electrical signals into optical signals, thereby transmitting optical signals over transmission media such as optical fibers. A vertical cavity surface emitting laser (VCSEL) component is often used as a laser optical source in an optical transmission device. The reliability of VCSEL components is very high, and the VCSEL components have high driving ability and can be arranged in a large array. The VCSEL components are mass-manufactured to reduce costs. In addition, VCSEL components may also emit laser beams having a very low laser critical current, single longitudinal mode, and low divergence. Accordingly, VCSEL components have become very important laser optical sources in fiber-optic communication and optical storage systems, especially high-speed, long-distance, fiber-optic communication systems.
The optical power output of a VCSEL component is proportional to the driving current thereof, and the optical power output may vary with the operating temperature. With the incensement of the operating temperature, the driving current of the VCSEL component should be increased, so that the optical power output of the VCSEL component under a higher operating temperature may reach the same optical power output of the VCSEL component under a lower operating temperature. Accordingly, a temperature compensation mechanism is desired to calibrate the driving current of the VCSEL component based on the variation of the operating temperature. The conventional temperature compensation mechanism may detect the operating temperature before calibrating the driving current. However, the driving current cannot be calibrated continuously instantly in accordance with different operating temperatures. In addition, in the conventional temperature compensation mechanism, the compensation effect, and efficiency may be limited because the current-to-temperature variation may be not large enough.